in situ immobilization of uranium in structured porous pacific … · 2005. 4. 27. · media via...

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Concept/Hypotheses Concept/Hypotheses ORIGINAL HYPOTHESIS: “Radionuclides in low-permeability porous matrix regions of fractured saprolite can be effectively isolated and immobilized by stimulating localized in-situ biological activity in highly-permeable fractured and microfractured zones within the saprolite.” (Roden and Scheibe, 2005) Field Site Development Field Site Development • Geophysical wells GP-1, GP-2, GP-3, GP-4 and GP-5 were recently completed. • Additional monitoring wells (blue in figure to the left) will be multi-level sampling (MLS) wells. Materials have been delivered and construction will begin soon. • Site infrastructure will then be complete. Wells FW212, FW213, and FW214 will serve as electron donor injection wells; flush experiment (tracer and water injection) will be conducted using FW215. In Situ Immobilization of Uranium in Structured Porous Media via Biomineralization at the Fracture/Matrix Interface (FRC Area 2 Field Project) The original hypothesis focused on the intact fractured saprolite zone INTACT SAPROLITE HAS ISSUES: Low U(VI) concentrations High nitrate concentrations Low permeability REVISED HYPOTHESIS: “In heterogeneous porous media, microbial activity can be stimulated at interfaces between zones of high and low groundwater flow rates in such a manner as to create a local, distributed redox barrier. Such a barrier will inhibit the transfer of contaminants from the low-flow zones that serve as long-term contaminant sources into the high-flow zones that transport contaminants to receptors.BROMIDE MISSING AT GOVERNMENT NUCLEAR RESERVATION Area 2 Tracer Test 10 Aug 04 IC data through 22 Sep 04 0 20 40 60 80 100 120 140 0 10 20 30 40 50 60 70 80 90 100 Elapsed Time (h) [Br]-mg/L - IC FW212 FW213 FW214 FW216-1 FW216-2 TPB16 GW835 FW202-2 DP13 Seep1 Seep2 Events FW215 - Injection Well 0 100 200 300 400 500 0 200 400 600 800 Bromide breakthrough curves from the Area 2 tracer test conducted August 2004. GRAVEL CAPTURES RESEARCHERS’ ATTENTION Vertical profiles of total sediment- associated uranium at two boreholes in Area 2. Gravel layer is at approximately 18 feet below ground surface. Saprolitic Fill Material Intact Saprolite Material Gravel Zone 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 0 10 20 30 40 50 60 Time (d) (mM) CH3CH2OH CH3COO- CH3CH2OH CH3COO 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 0 10 20 30 40 50 60 Time (d) NO3-, SO42- (mM) NO3- SO42- NO3 SO4 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 0 10 20 30 40 50 60 Time (d) Fe(II) (mmol/L) Total Dissolved Fe2Tot Fe2aq 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 0 10 20 30 40 50 60 Time (d) CH4, DIC (mM) CH4 CH4 DIC DIC Terminal Electron Accepting Processes (TEAPs) – Experimental and Model Results 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0 10 20 30 40 50 60 Time (d) U(VI) (mmol/L) Total UVITot 0.00 0.50 1.00 1.50 2.00 2.50 3.00 0 10 20 30 40 50 60 Time (d) U(VI)aq (uM) Total UVIaq U(VI) Partitioning and Reduction – Experimental and Model Results cDNA clone library (Total clones 41) Geobacter Oxalobacter Clostridium Dechloromonas Desulphosporinus Ferribacter Uncultured DNA clone library (total clones 30) Geobacter Oxalobacter Clostridium Dechloromonas Desulphosporinus Ferribacter Uncultured y = 0.4788x + 7.4456 R 2 = 0.3234 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 % Total Clones cDNA % Total Clones DNA FWB215 Slurry Experiments Slurry Experiments Tracer Test / Flush Experiment Tracer Test / Flush Experiment Timothy D. Scheibe Pacific Northwest National Laboratory, Richland, Washington, USA Eric E. Roden The University of Alabama, Tuscaloosa, Alabama, USA Scott C. Brooks Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA John M. Zachara Pacific Northwest National Laboratory, Richland, Washington, USA CRITICAL ISSUE: How to test hypothesis at the field scale? We added electron donor and saw U(VI) decrease… OK… But WHY? Hmmm.. .Did they account for the U(VI) coming in from up- gradient sources? EXPERIMENTAL CONCEPT: Flush Experiment for Mass Transfer Rate Determination Schematic diagram showing streamlines of injected water (with tracer) in dark blue and diverted streamlines under injection conditions of contaminated water flowing into the study zone from upgradient (red lines with arrows). The light blue circle represents the injection well (i.e., FW215) and dark green circles represent nearby monitoring points (FW212, FW213, FW214). Contours of hydraulic head are indicated by the grey lines. Accessible porosity within the zone of the aquifer encompassed by the blue streamlines is “flushed” of ambient contamination during the injection event. Any remaining solutes must then be provided from a local source (e.g., desorption and/or mass transfer from secondary porosity or an non-advective zone) Simulated (two cases) Observed Effect of Desorption Kinetics Observed Simulated Core/Well Data Core/Well Data Previous Cores GP01 – Geophysical Well Installed Feb. 2005 0.00 0.50 1.00 1.50 2.00 2.50 3.00 0 200 400 600 Total Fe (umol/g) Depth Below Top Boundary (ft) > 4000 2000-4000 1000-2000 106-1000 53-106 < 53 0.00 0.50 1.00 1.50 2.00 2.50 3.00 0 50 100 150 200 250 Total U (umol/g) Depth Below Top Boundary (ft) > 4000 2000-4000 1000-2000 106-1000 53-106 < 53 Above: Borehole flowmeter data from well GP-01. Total pumping rate = 2 L/min. Right: Map of experimental cell showing those wells with bromide breakthrough

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Page 1: In Situ Immobilization of Uranium in Structured Porous Pacific … · 2005. 4. 27. · Media via Biomineralization at the Fracture/Matrix Interface (FRC Area 2 Field Project) The

Concept/HypothesesConcept/Hypotheses

ORIGINAL HYPOTHESIS: “Radionuclides in low-permeability porous matrix regions of fractured saprolite can be effectively isolated and immobilized by stimulating localized in-situ

biological activity in highly-permeable fractured and microfractured zones within the saprolite.” (Roden and Scheibe, 2005)

Field Site DevelopmentField Site Development

• Geophysical wells GP-1, GP-2, GP-3, GP-4 and GP-5 were recently completed.

• Additional monitoring wells (blue in figure to the left) will be multi-level sampling (MLS) wells. Materials have been delivered and construction will begin soon.

• Site infrastructure will then be complete. Wells FW212, FW213, and FW214 will serve as electron donor injection wells; flush experiment (tracer and water injection) will be conducted using FW215.

In Situ Immobilization of Uranium in Structured Porous Media via Biomineralization at the Fracture/Matrix

Interface (FRC Area 2 Field Project)

The original hypothesis focused on the intact fractured saprolite zone

INTACT SAPROLITE HAS ISSUES:• Low U(VI) concentrations• High nitrate concentrations• Low permeability

REVISED HYPOTHESIS: “In heterogeneous porous media, microbial activity can be stimulated at interfaces between zones of high and low groundwater flow rates in such a

manner as to create a local, distributed redox barrier. Such a barrier will inhibit the transfer of contaminants from the low-flow zones that serve as long-term contaminant sources into the

high-flow zones that transport contaminants to receptors.”

BROMIDE MISSING AT GOVERNMENT NUCLEAR RESERVATION

Area 2 Tracer Test 10 Aug 04IC data through 22 Sep 04

0

20

40

60

80

100

120

140

0 10 20 30 40 50 60 70 80 90 100

Elapsed Time (h)

[Br]

-mg/

L - I

C

FW212

FW213FW214

FW216-1FW216-2

TPB16GW835

FW202-2

DP13

Seep1Seep2

Events

FW215 - Injection Well

0

100

200

300

400

500

0 200 400 600 800

Bromide breakthrough curves from the Area 2 tracer test conducted August 2004.

GRAVEL CAPTURES RESEARCHERS’ ATTENTION

Vertical profiles of total sediment-associated uranium at two boreholes in

Area 2. Gravel layer is at approximately 18 feet below ground surface.

Saprolitic Fill Material

Intact Saprolite Material

GravelZone

0.01.02.03.04.05.06.07.08.09.0

10.0

0 10 20 30 40 50 60

Time (d)

(mM

)

CH3CH2OHCH3COO-CH3CH2OHCH3COO

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 10 20 30 40 50 60

Time (d)

NO

3-, S

O42

- (m

M) NO3-

SO42-NO3SO4

0.02.04.06.08.0

10.012.014.016.018.020.0

0 10 20 30 40 50 60

Time (d)

Fe(II

) (m

mol

/L)

TotalDissolvedFe2TotFe2aq

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

0 10 20 30 40 50 60

Time (d)

CH4,

DIC

(mM

)

CH4CH4DICDIC

Terminal Electron Accepting Processes (TEAPs) –Experimental and Model Results

0.000.010.020.030.040.050.060.070.080.090.10

0 10 20 30 40 50 60

Time (d)

U(VI

) (m

mol

/L)

TotalUVITot

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0 10 20 30 40 50 60

Time (d)

U(VI

)aq

(uM

)

TotalUVIaq

U(VI) Partitioning and Reduction –Experimental and Model Results

cDNA clone library (Total clones 41)

Geobacter

Oxalobacter

Clostridium

Dechloromonas

Desulphosporinus

Ferribacter

Uncultured

DNA clone library (total clones 30)

Geobacter

Oxalobacter

Clostridium

Dechloromonas

Desulphosporinus

Ferribacter

Uncultured

y = 0.4788x + 7.4456R2 = 0.3234

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0

% Total Clones cDNA

% T

otal

Clo

nes

DNA

FWB215Slurry ExperimentsSlurry Experiments

Tracer Test / Flush ExperimentTracer Test / Flush Experiment

Timothy D. Scheibe Pacific Northwest National Laboratory, Richland, Washington, USA

Eric E. Roden The University of Alabama, Tuscaloosa, Alabama, USA

Scott C. Brooks Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA

John M. Zachara Pacific Northwest National Laboratory, Richland, Washington, USA

CRITICAL ISSUE: How to test hypothesis at the field scale?

We added electron donor and saw U(VI)

decrease…

OK… But WHY?

Hmmm.. .Did they account for the U(VI) coming in from up-gradient sources?

EXPERIMENTAL CONCEPT: Flush Experiment for Mass Transfer Rate Determination

Schematic diagram showing streamlines of injected water (with tracer) in dark blue and diverted streamlines under injection conditions of contaminated water flowing into the study zone from upgradient (red lines with arrows). The light blue circle represents the injection well (i.e., FW215) and dark green circles represent nearby monitoring points (FW212, FW213, FW214). Contours of hydraulic head are indicated by the grey lines.

Accessible porosity within the zone of the aquifer encompassed by the blue streamlines is “flushed” of ambient contamination during the injection event. Any remaining solutes must then be provided from a local source (e.g., desorption and/or mass transfer from

secondary porosity or an non-advective zone)

Simulated (two cases)

Observed

Effect of Desorption KineticsObserved

Simulated

Core/Well DataCore/Well DataPrevious Cores GP01 – Geophysical Well

Installed Feb. 2005

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0 200 400 600

Total Fe (umol/g)

Dep

th B

elow

Top

Bou

ndar

y (f

t)

> 4000

2000-4000

1000-2000

106-1000

53-106

< 53

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0 50 100 150 200 250Total U (umol/g)

Dep

th B

elow

Top

Bou

ndar

y (f

t)

> 4000

2000-4000

1000-2000

106-1000

53-106

< 53

Above: Borehole flowmeter data from well GP-01. Total pumping rate = 2 L/min.

Right: Map of experimental cell showing those wells with bromide breakthrough